Laminated core, vr type resolver and production method for laminated core

ABSTRACT

A production method for a rotor core for a VR type resolver has a structure in which one protrusion is formed on an inner edge thereof in which the rotor cores can be rotated and laminated without increasing cost. In a production method of a rotor core for a VR type resolver, a plurality of tabular rotor core pieces are laminated. In this case, in the rotor core pieces, four protrusions are simultaneously formed, one of them is left, the remainder thereof is removed, and rotating lamination is carried out.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation of application Ser. No. 14/301,818 filed Jun. 11,2014, which claims the benefit of Japanese Patent Application No.2013-135421 filed Jun. 27, 2013. The disclosure of the priorapplications is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a laminated core, a VR type resolverand a production method for the laminated core.

2. Description of Related Art

Japanese Unexamined Patent Application Laid-open No. 2013-72673discloses a rotor of a VR type resolver having a structure in which aprotrusion for fitting into a groove formed on a shaft is formed at oneportion on the inside. A rotor core of the VR type resolver has astructure in which a plurality of core forming members in a thin plateshape are laminated in an axial direction, in order to reduce iron loss.In the laminated structure, in order to secure the uniformity ofmagnetic characteristic in a circumferential direction, each of the thinmembers is laminated while gradually being rotated in a so-called“rotating lamination”. In addition, Japanese Unexamined PatentApplication Laid-open No. 2003-116252 discloses a press automaticrotating lamination of iron cores for a motor having a structure inwhich a key groove (concavity), but not a protrusion, is formed at oneportion on the inside.

In the technology described in Japanese Unexamined Patent ApplicationLaid-open No. 2003-116252, a plurality of iron cores (thin members forforming the core) are laminated while relatively rotating, so as toposition the key grooves, after the key grooves are simultaneouslyformed at different angular positions thereon and a punching process iscarried out. In this structure, it is necessary to form the key groovesat different angular positions, and therefore, there is a problem inthat the cost of used dies is increased or there is a problem in thatshapes or positions of the key grooves are shifted in the rotatinglamination.

In view of such circumstances, it is an object of the present inventionto provide a production method for a laminated core having a structurein which a protrusion is formed on the inside or the outside which doesnot increase cost and in which the protrusions are prevented fromshifting in rotating lamination.

SUMMARY OF THE INVENTION

A first aspect of the present invention has a laminated core having aprotrusion on an inner edge or an outer edge, wherein the protrusion andconcavities are formed on the same edge at fixed intervals. Thelaminated core includes a resolver, a rotor or a stator of a motor, orthe like.

A second aspect of the present invention has the laminated coreaccording to the first aspect, in which a plurality of tabular membersare rotated at fixed angular intervals and are laminated, the number ofprotrusions is one and the protrusion and the concavities are arrangedat even intervals. Here, the fixed angular intervals mean angularintervals in which tabular members for constituting the laminated coreare laminated while rotating in the rotating lamination. For example, inthe case in which a four-layer structure is obtained by the rotatinglamination, the tabular members are laminated while rotating every 90degrees.

A third aspect of the present invention has the laminated core accordingto the second aspect, in which the laminated core is a rotor core of aVR type resolver, the rotor core includes a magnetic pole portion havinga double axial angle NX, in which N is a natural number of 2 or more,and an opening at the center, the protrusion and the concavities areformed on the inner edge facing to the opening, the number ofprotrusions is one, and the number of the concavities is N-1.

A fourth aspect of the present invention has a VR type resolver containsa stator, and a rotor core according to the first aspect, in which therotor core is rotatably held to the stator.

A fifth aspect of the present invention has a production method of alaminated core contains a step for forming an opening in whichprotrusions are formed at even intervals, the number of the formedprotrusions is N and N is a natural number of 2 or more, a step forremoving the protrusions in which the number of the removed protrusionsis N-1 and one of the protrusions is left, a step for punching out anouter edge thereof, and a step for laminating iron cores of thelaminated cores produced by the above steps while matching positions ofthe protrusions.

According to the fifth aspect, since the rotating lamination is carriedout after removing the protrusions that are not finally required, theprotrusions can be simultaneously formed using one die, and theprotrusions can be prevented from shifting in rotating lamination.

A sixth aspect of the present invention has the production method of alaminated core according to the fifth aspect, in which the number of theformed protrusions (N) is 4, and the step for removing the protrusionsis carried out by two apparatuses having two punches for removing theprotrusions.

According to the present invention, in a production of the laminatedcore having a structure in which a protrusion is formed on the inside orthe outside, rotor cores having a protrusion can be rotated andlaminated without increasing cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view showing a processing apparatus for a rotor corein an embodiment of the present invention, and FIG. 1B is a side viewthereof.

FIGS. 2A to 2E are schematic views showing in a stepwise manner thesteps for producing the rotor core.

FIGS. 3A to 3D are schematic views showing in a stepwise manner thesteps for producing the rotor core.

FIGS. 4A and 4B are schematic views showing in a stepwise manner thesteps for producing the rotor core, and FIG. 4C is a side view showing alaminated core in which rotor core pieces are laminated.

FIG. 5 is a front view showing a rotor core piece.

FIG. 6 is a cross sectional view in an axial direction showing a VR typeresolver.

PREFERRED EMBODIMENTS OF THE INVENTION Processing Apparatus

FIG. 1 shows a processing apparatus 100 for a rotor core (an example oflaminated cores) of a VR type (a variable reluctance type) resolver. Theprocessing apparatus 100 is used for processing electrical steels, so asto produce rotor core pieces that constitute the rotor core. The rotorcore is produced by laminating the rotor core pieces that were processedby the processing apparatus 100. In this laminating, a rotatinglamination is carried out. Here, the electrical steel is used as amaterial that constitutes the rotor core; however, other magneticmaterials can also be used. The rotor core explained in this embodimenthas a double axial angle 4X. The rotor core of the VR type resolverhaving a double axial angle 4X has a nearly circular shape having fourmagnetic pole portions that protrude radially from an axial center, soas to obtain power for four cycles while the rotor core rotates onecycle. The magnetic pole portions are formed at even intervals, and inthe case of a double axial angle 4X, they are formed at angularintervals of 90 degrees.

The processing apparatus 100 includes an apparatus A for punching outthe magnetic steel using an inner die 101, an apparatus B for punchingit out using punches 102 a and 102 b, an apparatus C for punching it outusing punches 103 a and 103 b, and an apparatus D for punching it outusing on outer die 104, viewed from a left side of FIG. 1. Theseapparatuses are arranged at even intervals. Specifically, the inner die101 of the apparatus A is a die for forming an opening at the center ofthe rotor core. The inner die 101 has a nearly round shape, andconcavities 101 a, 101 b, 101 c and 101 d are formed on the outer edgethereof. The concavities 101 a to 101 d are formed at angular positionsevery 90 degrees (that is, at clock positions 0:00, 3:00, 6:00, and9:00). The inner die 101 is moved forward and backward in a depthdirection of FIG. 1A (in a perpendicular direction of FIG. 1B). Anelectrical steel 200 described below (see FIGS. 2A to 2E) is punched outby the inner die 101, and for example, an opening in a nearly roundshape represented by reference numeral 201 in FIGS. 2A to 2E is formed.

The punch 102 a in the apparatus B is a punch for removing a protrusion201 a formed by a concavity 101 a of the inner die 101, and the punch102 b in the apparatus B is a punch for removing a protrusion 201 cformed by a concavity 101 c of the inner die 101. With respect to thepunches 102 a and 102 b, both of them may be simultaneously used, andonly one of them may be used after the other is fed (retracted) towardthe axial center.

The punch 103 a in the apparatus C is a punch for removing a protrusion201 d formed by a concavity 101 d of the inner die 101, and the punch103 b in the apparatus C is a punch for removing a protrusion 201 bformed by a concavity 101 b of the inner die 101. With respect to thepunches 103 a and 103 b, both of them may be simultaneously used, andonly one of them may be used after the other is fed (retracted) towardthe axial center.

The outer die 104 in the apparatus D is a die for forming an outer shapeof a thin member for forming the rotor core (a rotor core piece). Acenter opening is formed by the inner die 101, and an outer portionthereof is punched out by the outer die 104, whereby, rotor core pieces211, 212, 213 and 214 shown in FIGS. 2 and 4 are obtained. A rotor core410 in FIG. 6 is produced by laminating a plurality of the rotor corepieces while turning in an axial direction. Here, the axis is a rotationaxial center of the rotor core, and the axial direction is a directionin which a rotation axis of the rotor core extends.

In a final step of the processing apparatus 100, a rotation stage 120 isprovided. The rotation stage 120 is arranged and rotated under theapparatus D, so that the rotor core pieces punched out by the outer die104 of the apparatus D are automatically placed thereon. That is, therotor core pieces punched out by the outer die 104 automatically fall ina perpendicular direction, and are placed on the rotation stage 120. Forexample, when the rotor core pieces are already placed on the rotationstage 120, the rotor core pieces on the rotation stage 120 can belaminated by the falling of the next rotor core piece punched out by theouter die 104 on top of them. In addition, the rotor core pieces can belaminated while rotating by rotating the rotation stage 120.

Assembly

In the following, an example of steps for producing the rotor core willbe explained. FIGS. 2A to 2E, 3A to 3D and 4A to 4B show in a stepwisemanner the steps for producing the rotor core. An elongated electricalsteel 200 is prepared. In this electrical steel 200, a cavity (notshown) is formed by embossing as a positioning means for the processingapparatus 100. In addition, a protrusion (not shown) for engaging thepositioning means on the electrical steel 200 is formed on theprocessing apparatus 100, whereby the electrical steel 200 is positionedfor the processing apparatus 100. Furthermore, an opposite surface ofthe above cavity formed on the electrical steel 200 is formed in aconvex shape, and each of the rotor core pieces to be laminated on therotation stage 120 is positioned using this uneven structure.

The long electrical steel 200 is processed while being sequentially fedfrom left to right of the processing apparatus 100 in FIG. 1. Here,although there are steps after FIG. 4B, the steps after FIG. 4B are notillustrated (of course it may be completed at the step of FIG. 4B).

First, the processing shown in FIG. 2A is carried out. A right end ofthe electrical steel 200 is placed on the apparatus A arranged at a leftend of the processing apparatus 100. The opening 201 is formed bypunching out the electrical steel 200 using the inner die 101. On theinner edge of the opening 201, a protrusion 201 a is formed by aconcavity 101 a of the inner die 101, a protrusion 201 b is formed by aconcavity 101 b, a protrusion 201 c is formed by a concavity 101 c, anda protrusion 201 d is formed by a concavity 101 d. The protrusions 201a, 201 b, 201 c and 201 d have a protruding structure that protrudestoward a direction of an axial center (center of the opening 201), andthey are formed at angular intervals of 90 degrees, respectively.

A processing shown in FIG. 2B is carried out after a state shown in FIG.2A is obtained. In this process, the electrical steel 200 is further fedfrom the state shown in FIG. 2A to a right direction of the figure, andthe center of the opening 201 matches the center of the apparatus B. Theprotrusions 201 a and 201 c are simultaneously removed using the punches102 a and 102 b. In this case, it is preferable that removing positionsagree with the inner edge of the opening 201 as exactly as possible;however, the protrusions 201 a and 201 c are sufficiently removed, sothat burrs do not occur from the inner edge of the opening 201 towardthe axial center. Therefore, the inner edge of the opening 201 isslightly cut at portions at which the protrusions 201 a and 201 c areremoved, and small concavities are formed thereat as marks of removal.In FIG. 2, these concavities are not shown. FIG. 5 shows a state inwhich concavities 221 and 223 formed when the protrusions 201 a and 201c are removed by the punches 102 a and 102 b are exaggerated. Aconcavity 222 is a mark of removal of the protrusion 201 b removed bythe following process. The concavity that is a mark of removal of thisprotrusion is formed in the same manner as that in another openingdescribed below.

In the processing shown in FIG. 2B, the electrical steel 200 is punchedout at the same timing at which the apparatus B performs processing,using the inner die 101 of the apparatus A, and whereby, an opening 202is formed at a left side of the opening 201. The opening 202 has thesame shape as that of the opening 201, and the protrusions 202 a, 202 b,202 c and 202 d are formed on the inner edge.

After the state shown in FIG. 2B is obtained, the electrical steel 200is fed in a right direction of the figure in the processing apparatus100, and a step shown in FIG. 2C is carried out. In this process, thecenter of the opening 201 is matched with the center of the apparatus C.At this time, since each apparatus in the processing apparatus 100 isarranged at even intervals, the center of the opening 202 is matchedwith the center of the apparatus B. The protrusion 201 b of the opening201 is removed by using the punch 103 b in a state in which the punch103 a of the apparatus C is retracted. That is, the protrusion 201 d isleft without being removed. At the same timing as that in which thisapparatus C performs processing, the protrusion 202 c of the opening 202is removed by using the punch 102 b in a state in which the punch 102 aof the apparatus B is retracted. That is, the protrusion 202 a is leftwithout being removed. At the same timing as that in which the apparatusC and the apparatus B perform processing, an opening 203 is formed at aleft side of the opening 202 using the inner die 101 of the apparatus A.The opening 203 has the same shape as that of the openings 202 and 201,and protrusions 203 a, 203 b, 203 c and 203 d are formed on the inneredge.

After the state shown in FIG. 2C is obtained, the electrical steel 200is fed in a right direction of the figure in the processing apparatus100, and a step shown in FIG. 2D is carried out. In this process, thecenter of the opening 201 is matched with the center of the apparatus D.At this time, since each apparatus in the processing apparatus 100 isarranged at even intervals, the center of the opening 202 is matchedwith the center of the apparatus C, and the center of the opening 203 ismatched with the center of the apparatus B. The outside of the opening201 is punched out using the outer die 104 of the apparatus D, and rotorcore pieces 211 in a nearly circular shape including four magnetic poleportions which protrude from an axial center toward a radical direction,are obtained. The rotor core pieces 211 fall and are placed on therotation stage 120 arranged under the apparatus D.

This state is shown in FIG. 2E. In FIG. 2E, a punching mark 251 formedby punching out using the apparatus D, is shown. In FIG. 2E, therotation stage 120 is described at a right side of the processingapparatus 100 from the viewpoint of drawing (actually, the rotationstage 120 is placed under the processing apparatus 100, as shown in FIG.1). This is the same in FIGS. 3 and 4.

At the same timing at which this apparatus D processes, the protrusions202 d and 202 b are removed by using the punches 103 a and 103 b of theapparatus C. In addition, at the same timing at which the apparatus Dand the apparatus C perform processing, the protrusions 203 a and 203 con the edge of the opening 203 is removed by using the punches 102 a and102 b of the apparatus B. Furthermore, at the same timing at which theapparatus D, the apparatus C and the apparatus B perform processing, anopening 204 is formed by using the inner die 101 of the apparatus A. Theopening 204 has the same shape as those of the openings 201 to 203, andthe protrusions 204 a, 204 b, 204 c and 204 d are formed on the inneredge thereof.

In the state shown in FIG. 2E, the rotation stage 120 is rotatedclockwise by 90 degrees. Specifically, the protrusion 201 d of the rotorcore piece 211 punched out by the apparatus D is formed in a directionof 9:00 o'clock, and the rotor core piece 211 is placed on the rotationstage 120 in this state (a state shown in FIG. 2D). Then, the protrusion201 d is positioned in a direction for 0:00 o'clock by rotatingclockwise by 90 degrees the rotation stage 120.

The electrical steel 200 is fed to a right direction in the figure,after the rotor core piece 211 is rotated clockwise by 90 degrees fromthe state shown in FIG. 2E, and a step shown in FIG. 3A is performed. Inthis process, the center of the opening 202 is matched with the centerof the apparatus D. In this case, since each apparatus of the processingapparatus 100 is arranged at even intervals, the center of the opening203 is matched with the center of the apparatus C, and the center of theopening 204 is matched with the center of the apparatus B. In thisstate, the rotor core piece 211 in which the protrusion 201 d isarranged at a position for 0:00 o'clock, is placed on the rotation stage120.

Then, the rotor core piece 212 is obtained by punching out an outerportion of the opening 202 using the outer die 104 of the apparatus D.The rotor core piece 212 has the same shape as that of the rotor corepiece 211 (a shape which agrees therewith when rotating), and falls andis placed on the rotation stage 120 arranged under the apparatus D. Atthis time, the stator core piece 12 is laminated on the stator corepiece 211 by having a shape in which the protrusions are combined, sincethe rotor core piece 211 in which the protrusion 201 d is fed in adirection for 0:00 o'clock is placed on the rotation stage as shown inFIG. 3A. This state is shown in FIG. 3B. In FIG. 3B, a punching mark 252formed by punching out using the apparatus D is shown.

At the same timing at which this apparatus D processes, the protrusion203 d is removed by using the punch 103 a of the apparatus C. Inaddition, at the same timing at which the apparatus D and the apparatusC perform processing, the protrusion 204 a on the inner edge of theopening 204 is removed by using the punch 102 a of the apparatus B.Furthermore, at the same timing at which the apparatus D, the apparatusC and the apparatus B perform processing, an opening 205 is formed byusing the inner die 101 of the apparatus A. The opening 205 has the sameshape as those of the openings 201 to 204, and protrusions 205 a, 205 b,205 c and 205 d are formed on the inner edge thereof.

On the rotation stage 120, the rotor core piece 212 is laminated on therotor core piece 211, so that a state shown in FIG. 3B is obtained, andthen the rotation stage 120 is rotated clockwise by 90 degrees. Theprotrusions 201 d and 202 a are positioned in a direction for 3:00o'clock by this rotation.

Next, a step shown in FIG. 3C is carried out. In this process, thecenter of the opening 203 is matched with the center of the apparatus D.At this time, since each apparatus of the processing apparatus 100 isarranged at even intervals, the center of the opening 204 is matchedwith the center of the apparatus C, and the center of the opening 205 ismatched with the center of the apparatus B. Then, an outer portion ofthe opening 203 is punched out by using the outer die 104 of theapparatus D, and a rotor core piece 213 is obtained. The rotor corepiece 213 has the same shape as those of the rotor core pieces 211 and212 (a shape which agrees therewith when rotating), and it fallsdownward by being punched out using the outer die 104, and it is placedon the rotation stage 120 arranged under the apparatus D. At this time,the rotor core pieces 211 and 212 in which the protrusions are fed in adirection for 3:00 o'clock are placed on the rotation stage 120, andtherefore, the rotor core pieces 211, 212 and 213 are laminated byhaving a shape in which the protrusions are combined. This state isshown in FIG. 3D. In FIG. 3D, a punching mark 253 formed by punching outusing the apparatus D, is shown.

At the same timing in which this apparatus D performs processing, theprotrusions 204 d and 204 b are removed by using the punches 103 a and103 b of the apparatus C. In addition, at the same timing at which theapparatus D and the apparatus C perform processing, the protrusions 205a and 205 c are removed by using the punches 102 a and 102 b of theapparatus B. Furthermore, at the same timing at which the apparatus D,the apparatus C and the apparatus B perform processing, an opening 206is formed by using the inner die 101 of the apparatus A. The opening 206has the same shape as those of the openings 201 to 205, and protrusions206 a, 206 b, 206 c and 206 d are formed on an inner edge thereof.

Next, in the state shown in FIG. 3D, the rotation stage 120 is rotatedclockwise by 90 degrees. The overlapped three protrusions 201 d, 202 aand 203 b are positioned at 6:00 o'clock by this rotation (see FIG. 4A).

Next, a step shown in FIG. 4A is carried out. In this process, thecenter of the opening 204 is matched with the center of the apparatus D.At this time, since each apparatus of the processing apparatus 100 isarranged at even intervals, the center of the opening 205 is matchedwith the center of the apparatus C, and the center of the opening 206 ismatched with the center of the apparatus B. Then, an outer portion ofthe opening 204 is punched out by using the outer die 104 of theapparatus D, and a rotor core piece 214 is obtained. The rotor corepiece 214 has the same shape as those of the rotor core pieces 211, 212and 213 (a shape which agrees when rotating), and it falls downward bythe action of the outer die 104 and is placed on the rotation stage 120arranged under the apparatus D. At this time, the rotor core pieces 211,212, 213 and 214 are laminated in a shape in which the protrusions arecombined, since on the rotation stage 120 the rotor core pieces 211, 212and 213 in which the protrusions are fed in a direction of 6:00 o'clockare placed. This state is shown in FIG. 4B. In FIG. 4B, a punching mark254 formed by punching out using the apparatus D is shown.

At the same timing at which the apparatus D performs processing, theprotrusion 205 b is removed by using the punch 103 b of the apparatus C.In addition, at the same timing at which the apparatus D and theapparatus C perform processing, the protrusion 206 c is removed by usingthe punch 102 b of the apparatus B. Furthermore, at the same timing atwhich the apparatus D, the apparatus C and the apparatus B performprocessing, an opening 207 is formed by using the inner die 101 of theapparatus A. The opening 207 has the same shape as those of the openings201 to 206, and protrusions 207 a, 207 b, 207 c and 207 d are formed onan inner edge thereof.

The four rotor core pieces 211, 212, 213, and 214 are rotated by 90degrees and are laminated by the above process, whereby a laminated body303 is obtained. In this rotating lamination, each the rotor core pieceis fixed by caulking using dowel protrusions formed on the surfacethereof (not shown) and concavities formed on the rear surface thereof(not shown), so as to obtain the laminated body. The number of the rotorcore pieces to be laminated is not limited. However, for example, whenthe rotor core is obtained by rotating lamination of the four rotor corepieces 211, 212, 213 and 214, the laminated body 303 forms a rotor core.

The rotor core pieces are further laminated by repeating the aboveprocess. Here, actions of each punch are regular and repeatedly avoidand cut. In the following, these actions are specifically explained byusing the punch 102 a of the apparatus B. The process shown in FIG. 2Bcuts the protrusion, the process shown in FIG. 2C avoids the protrusion,the process shown in FIG. 2D cuts the protrusion, the process shown inFIG. 3A cuts the protrusion, the process shown in FIG. 3C cuts theprotrusion, and the process shown in FIG. 4A avoids the protrusion. Thatis, the protrusion is avoided one in four times. This ratio can becarried out in any punch.

It is preferable that the center of the magnetic pole portion formed onan outer edge of the rotor core (the most protruded portion) be matchedwith the center of the protrusion and that the concavity be formed on aninner edge thereof. For example, when the protrusion and the concavityare formed at a boundary between the magnetic pole portions, except forthe center of the magnetic pole portion, magnetic characteristics in therotor core are affected, and detection accuracy and detection level aredecreased.

The number of the rotor core pieces to be laminated is not limited, andthe number can be optionally selected. In the above process, first, oneof the four protrusions simultaneously formed is left, and the remainingthree protrusions are removed. The rotor core pieces are laminated whilerotating at 90 degrees so that the left protrusions are placed atangular positions every 90 degrees. In this way, each protrusion of therotor core pieces is positioned, and the rotating lamination is carriedout without overlapping the same positions.

The apparatus B and the apparatus C for removing the protrusionsexplained by the above process have two punches, respectively. However,an apparatus having four punches in which the apparatus B and theapparatus C are combined may be arranged between the apparatus A and theapparatus D. In this case, according to the apparatus having fourpunches, one protrusion is sheltered from the punch and the remainingthree protrusions are removed by the punch. The protrusions to beremoved are rotated as the processing progresses. In addition, fourapparatus having one punch, respectively, may be placed between theapparatus A and the apparatus B.

Laminated rotor cores in which protrusions are formed on an outer edgeare very similar to laminated rotor cores in which protrusions areformed on an inner edge. In the following, a summary will be given. Aplurality of concavities is formed on the outer die 104 of the apparatusD, as explained for the apparatus A. When the electrical steel ispunched out in a state without a concavity, a plurality of protrusionsis formed on the outer edge. In contrast, according to the presentinvention, an opening is formed on the inner edge by the apparatus A. Inthe punching process in the apparatus B and the apparatus C, punches areplaced at portions in which protrusions are formed, and portions inwhich the protrusions are removed are punched out by round openings orsquare openings. Portions in which the protrusions are formed are notpunched out. Then, the outer edge is punched out by the apparatus D. Asa result, protrusions are not formed at portions at which the roundopenings or square openings were already formed, and protrusions areformed at portions at which processing was carried out. The punched outrotor cores are placed and rotated on the rotation stage.

FIG. 6 shows a cross sectional view in an axial direction of a VR typeresolver using the rotor cores produced by the above process. In FIG. 6,the VR type resolver 400 is shown. The VR type resolver 400 has a statoryoke 401. The stator yoke has a nearly tubular structure in which a thinmagnetic material, such as an electrical steel, is punched out in ashape as shown, and it is laminated in an axial direction.

The stator yoke 401 has salient poles 402 to 405 that protrude towardthe axial center. For example, exciting coils (not shown) are woundaround the salient poles 402 to 405, respectively, sine phase detectioncoils (not shown) are wound around the salient poles 402 and 404,respectively, and cosine phase detection coils (not shown) are woundaround the salient poles 403 and 405, respectively.

A rotor 410 rotatably held to the stator yoke 401 is placed at theinside of the stator yoke 401. The rotor 410 has a structure in which arotor core 411 and a shaft 421 are combined.

The rotor core 411 has a structure in which a plurality of rotor corepieces are laminated by methods shown in FIGS. 2 to 4. The rotor core411 has an opening 412, and a protrusion 413 that protrudes in an axialdirection and concavities 414, 415 and 416 are formed at a portionfacing to the opening 412 (an inner edge). The protrusion 413 has astructure in which a cross sectional shape as shown extends in an axialdirection. The concavities 414, 415 and 416 correspond to theconcavities 221, 222 and 223 shown in FIG. 5, and have a structure inwhich a cross sectional shape as shown extends in an axial direction.The protrusion 413 and the concavities 414, 415 and 416 are arranged ateven intervals (even angular positions) in a circumferential direction.

In the shaft 421, the concavity 422 having a shape that matches theprotrusion 413 is formed. A rotation stopping structure of the rotorcore 411 to the shaft 421 can be obtained by combining the rotor core411 with the shaft 421 in a state in which the protrusion 413 is matchedwith the concavity 422.

Advantages

In one rotor core piece, four protrusions are simultaneously formedusing one die. Therefore, the present invention can avoid a problem inthat cost of the die is increased and a problem in that shapes andpositions of protrusions are shifted in rotating lamination. Therotating lamination is carried out by laminating the rotor core pieceswhile rotating in order, whereby the uniformity of the magneticcharacteristics in a circumferential direction can be ensured. That is,four protrusions are formed on one rotor core piece, and one protrusionthereof is left. Then, the rotating lamination is carried out byrotating and laminating the rotor core pieces so as to shift the leftprotrusions by every 90 degrees, whereby the positions of theprotrusions can be matched.

The protrusions 201 a, 201 b and 201 c are removed by the punches sothat the concavities 221, 222 and 223 that are marks of removal shown inFIG. 5, are formed. In this way, an obstruction when combining with theshaft 421, will not remain. When the protrusions are left, anotherprocess for removing them is further required, and manufacturing cost isincreased. In contrast, according to the present invention, theadditional process can be omitted and the production cost can bedecreased, by removing the protrusions 201 a, 201 b and 201 c using thepunch, so as to form concavities 221, 222 and 223.

Other Matters

In the above embodiments, double axial angles are 4X. However, thenumber of double axial angles is not limited to 4X. For example, in thecase in which the shaft double angle is 5X, the protrusions are formedat angular intervals of every 72 degrees, and one thereof is left andthe other is removed. Then, the rotor core pieces are laminated whilerotating by every 72 degrees. In this case, positions of protrusions tobe left are selected so as to match the position of the protrusions whenlaminating while rotating at 72 degrees.

In addition, in the above embodiment, the process in which four rotorcore pieces are laminated was explained; however, the number of thelaminated rotor core pieces is not limited to four layers. The number ofthe protrusions is not limited to one. The laminated core may be astator. The laminated core is not limited to use for a resolver, and itmay be used for a rotor of a motor or a stator.

The embodiments of the present invention are not limited to each of theabove embodiments and include various modifications that may beanticipated by one skilled in the art. In addition, the effects of thepresent invention are also not limited to the description above. Thatis, various additions, changes, and partial deletions can be made in arange that does not exceed the general concept and object of the presentinvention as claimed in the Claims and equivalents thereof.

What is claimed is:
 1. A production method of a rotor core, comprising astep for forming one protrusion at each inner edges of a plurality oftubular members, and a step for forming concavities at inner each theedges of the tubular members, a step for laminating the tabular membersin an axis direction, wherein a rotor core comprises the tabularmembers, wherein the tabular members include the inner edges, the oneprotrusion and the concavities are arranged at the inner edges of thetabular members in a radial direction and arranged with a predeterminedinterval in a circumferential direction.
 2. The production method of arotor core according to claim 1, wherein the rotor core comprises amagnetic pole portion, wherein the magnetic pole portion includes adouble axial angle NX, N is a natural number of 2 or more, and thenumber of concavities is N-1.
 3. The production method of a rotor coreaccording to claim 1, wherein a step for removing the protrusions inwhich the number of removed protrusions is N-1 and one of theprotrusions is left, a step for punching out an outer edge thereof, anda step for laminating iron cores of the laminated cores produced by theabove steps while matching positions of the protrusions.
 4. Theproduction method of a rotor core according to claim 3, wherein: thenumber of the formed protrusions (N) is 4, and the step for removing theprotrusions is carried out by two apparatuses having two punches forremoving the protrusions.
 5. A rotor core comprising: a plurality oftabular members including an inner edge, wherein the tabular members arelaminated, in an axis direction and one protrusion and a plurality ofconcavities are arranged inside each of the inner edges of the tabularmembers in a radial direction, and arranged with a predeterminedinterval in a circumferential direction.
 6. The rotor core according toclaim 5, comprising: a magnetic pole portion, wherein the magnetic poleportion includes a double axial angle NX, in which N is a natural numberof 2 or more, and an inner edge, the number of concavities is N-1. 7.The laminated core according to claim 5, comprising: a first tabularmember and a second tabular member that are laminated with each other,wherein: the first tabular member has one protrusion among the pluralityof protrusions and one concavity among the plurality of concavities, thesecond tabular member has another one protrusion and another pluralityof concavities, and the one protrusions and the plurality of concavitiesare arranged with a fixed interval.
 8. A resolver comprising: a stator,and a rotor claim 5, wherein the rotor core is rotatably held to thestator.